Thermoplastic shaped bodies with segments of varying rigidity

ABSTRACT

The shaped article consists of 
     a) from 5 to 95% by weight of a molding composition A made from at least one thermoplastic polyamide, copolyamide or blends of these as component A1, fillers and/or reinforcing materials, if desired, as component A2, impact modifiers as component A3 and other additives and processing aids as component A4, and 
     b) from 5 to 95% by weight of a molding composition B, made from at least one thermoplastic polyamide, copolyamide or blends of these as component B1, at least one crosslinked elastomeric polymer as component B2 and, if desired, other additives and processing aids as component B3, 
     where, in the shaped article, segments of molding compositions A and B are connected to one another over a relatively large area. These shaped articles may be used in the motor vehicle sector, for example as air or coolant ducts.

The invention relates to thermoplastic shaped articles, in particularhollow shaped articles, composed of hard and soft segments, processesfor producing them by injection molding, extrusion and extrusion blowmolding and the use of molding compositions A and B for producing theshaped articles.

Nowadays, blow molding is very widely used for producing hollow shapedarticles. For this process, the tube is extruded into the opened moldand expanded, and the mold is then closed. Portions of the plasticmaterial which extend beyond the required shape are pinched off and,after demolding, are removed as flash, which has to be recycled. Theresultant moldings have an encircling pinch-off line, and this is apoint of weakness.

Nowadays, 3-dimensional blow molding provides an advanced process forproducing moldings of complicated geometry which have no pinch-off line.In contrast to the process described above, protruding portions of theplastic material which must be pinched off and removed as flash ariseonly at the two ends of the tube or parison. This process also avoidsthe formation of longitudinal pinch-off lines and is described, forexample, in DE-A 37 18 605.

To produce moldings having a combination of materials which alternate inthe longitudinal direction, it is advantageous to combine this processwith sequential coextrusion. For this, the extrusion die is fedalternately from a number of extruders with different materials duringextrusion of the parison, giving a tube having segments of differingconstruction and material properties. By this means it is possible, forexample, to produce in a single operation blow moldings having flexibleend zones and a rigid middle section. Until now, parts of this type hadto be produced by complicated assembly of many sections.

For coextrusion, good adhesion of the components to one another isnecessary. It is therefore advantageous not to switch completely fromone component to the other, but just to vary the wall thickness ratio sothat in every region of the molding there are layers of both components.The two components are thus mutually connected over a relatively largearea and this improves their adhesion.

A further requirement for good adhesion is good compatibility of thecomponents with one another.

Moldings having alternating property combinations are used in automotiveconstruction and mechanical engineering. It is possible, for example, toaccommodate within a pipe, a charge-air pipe for a turbodiesel enginefor a vehicle, for example, segments for damping and heat expansion. Formany applications moreover, the parts must have good heat resistance andgood chemical resistance, for example to resist contamination by oil,and therefore both components must have these properties, since theperformance of a part composed of a number of components is limited byits weakest component.

EP-B 0 393 409 describes shaped articles composed of a number ofsections which are connected via limited areas of contact, thesubsections consisting of, respectively, a polyolefin-modified polyamide(a polyamide mixed with a polyolefin functionalized with carboxyl oranhydride groups) and of a polyolefin. The sections are connected byinjection-molding or extruding one component onto a hardened subsectioncomposed of the other component. The adhesion of the, per seincompatible, polymers of the subsections of the shaped article isattributable to the compatibilizing effect of the functionalizedpolyolefin.

EP-A 0 659 534 discloses sequentially extruded coolant pipes having anouter layer of high bursting strength and an inner layer which is inertto coolants and does not swell, the outer layer consisting of apolyamide and the inner or intermediate layer, which is compatible withthe outer layer, consisting of polyolefins modified with carboxyl oranhydride groups.

According to EP-A 0 659 535, these coolant pipes may be produced byextrusion blow molding combined with 3D manipulation of the parison.

A disadvantage with these moldings is the use of layers of polyolefincomponents having comparatively low heat resistance. It is an object ofthe present invention to provide thermoplastic moldings havingalternating hard/soft segments, where the soft segments, besides highflexibility, also have in particular high chemical resistance and heatresistance, and where there is also good adhesion to a hard segmentconsisting essentially of polyamide. It is a further object of theinvention to provide moldings having segments of differing stiffnesscomposed of components connected to one another over a relatively largearea, where each of the components has high heat resistance and highheat aging resistance, high long-term service temperature, high chemicalresistance, in particular high resistance to oil, fuel and coolants, andhigh tensile and/or bursting strength.

We have found that this object is achieved by means of shaped articlescomposed of

a) from 5 to 95% by weight of a molding composition A composed of

a1) from 40 to 100% by weight of at least one thermoplastic polyamide,copolyamide or blends of these as component A1,

a2) from 0 to 60% by weight of fillers and/or reinforcing materials ascomponent A2,

a3) from 0 to 20% by weight of impact modifiers as component A3 and

a4) from 0 to 30% by weight of other additives and processing aids ascomponent A4,

where the total of the amounts of components A1 and, if used, A2 to A4,is 100% by weight,

b) from 5 to 95% by weight of a molding composition B composed of

b1) from 20 to 79.9% by weight of at least one thermoplastic polyamide,copolyamide or blends of these as component B1,

b2) from 20.1 to 80% by weight of at least one crosslinked elastomericpolymer as component B2 and

b3) from 0 to 30% by weight of other additives and processing aids ascomponent B3,

where the total of the amounts of components B1, B2 and, if used, B3 is100% by weight,

where, in the shaped article, segments of the molding compositions A andB are connected to one another over a relatively large area.

It has been found that when a highly crosslinked elastomeric polymer isused in a mixture with a polyamide, even when there is a high proportionof the elastomeric polymer in the mixture, the continuous phase isformed by the polyamide. The polymer proportion results in a softcomponent (molding composition B) which also has the properties of thepolyamide, in particular high heat resistance, chemical resistance,tensile and bursting strength, and at the same time is compatible withthe hard component (molding composition A) composed of polyamide.

Molding Composition A

Molding composition A is built up from

a1) from 40 to 100% by weight of at least one thermoplastic polyamide,copolyamide or blends of these as component A1,

a2) from 0 to 60% by weight of fillers and/or reinforcing materials ascomponent A2,

a3) from 0 to 20% by weight of impact modifiers as component A3 and

a4) from 0 to 30% by weight of other additives and processing aids ascomponent A4,

where the total of the amounts of components A1 and, if used, A2 to A4,is 100% by weight.

The molding compositions A comprise, as component A1, from 40 to 100% byweight, preferably from 70 to 100% by weight, particularly preferablyfrom 85 to 100% by weight, of a thermoplastic polyamide, copolyamide orblends of these.

The polyamides which may be used are known per se. Examples of these arepolyhexamethylene adipamide, polyhexamethylene pimelamide,polyhexamethylene suberamide, polyhexamethylene azelamide,polyhexamethylene sebacamide, polyhexamethylene dodecanediamide,polyoctamethylene suberamide, polydodecamethylene dodecanediamide,poly-11-aminoundecanamide and bis-(4-aminocyclohexyl)methanedodecanamideor the products obtained by ring-opening of lactams, eg. polycaprolactamor polylaurolactam. Other suitable polyamides are those based onterephthalic or isophthalic acid as acid component and/ortrimethylhexamethylenediamine, bis(4-aminocyclohexyl)methane or2,2-di(4-aminocyclohexyl)propane as diamine component and polyamide baseresins prepared by copolymerizing two or more of the abovementionedpolymers or their components, for example copolycondensates ofterephthalic acid, hexamethylenediamine and caprolactam (nylon-6,T/6),and of terephthalic acid, isophthalic acid, adipic acid andhexamethylenediamine (nylon-6,T/6,I), which may also be built up asternary copolycondensates with other polyamide-forming monomers: eg.with adipic acid (nylon-6,I/6,T/6,6) or with alicyclic diamines, such asbis(4-aminocyclohexyl)methane or bis(4-amino-3-methylcyclohexyl)methane.

Use is preferably made of partially crystalline polyamides,preferentially nylon-6, nylon-6,6, nylon-6,T/6, nylon-6/6,T,nylon-6,T/6,1, nylon-6,T/6,6, nylon-6,T/6,I/6,6, nylon-6,6/6,T(copolycondensates of hexamethylenediamine, adipic acid, caprolactam andiso- and/or terephthalic acid) and nylon-4,6. It is also possible to usemixtures of different polyamides. It is particularly preferable to usenylon-6,6 and nylon-6, in particular nylon-6.

In one embodiment of the invention, the viscosity number of component A1is from 130 to 500, preferably from 140 to 400. The viscosity numbersare usually determined according to ISO 307 using 0.5% strength byweight solutions in 96% strength by weight sulfuric acid at 25° C.

The molding composition A may contain, as component A2, up to 60% byweight, preferably from 10 to 30% by weight, particularly preferablyfrom 10 to 20% by weight, of a filler or reinforcing material.Preference is given to fibrous reinforcing materials, such as glassfibers, carbon fibers, aramid fibers and potassium titanate fibers.Glass fibers, in particular glass fibers of E glass, are particularlypreferred.

Other substances which may be present as component A2, alone or in amixture with the fibrous reinforcing materials mentioned, are mineralfillers, such as wollastonite, kaolin, quartz, mica and calciumcarbonate.

The fillers and/or reinforcing materials are preferably treated with acoupling agent, such as alkylaminoalkoxysilane. In a particularlypreferred embodiment of the invention, component A2 consists exclusivelyof glass fibers.

The molding composition A may contain, as component A3, up to 20% byweight of impact modifiers. Impact modifiers are polyolefins which havebeen grafted with reactive groups, and are known per se. Examples ofsuitable impact modifiers are described in U.S. Pat. No. 4,174,358,column 6, line 21 to column 7, line 26.

The molding composition A may contain, as component A4, up to 30% byweight of other additives and processing aids. The proportion of theseis preferably up to 10% by weight, based on the total weight ofcomponent A.

Examples of usual additives are stabilizers and oxidation inhibitors,heat stabilizers and UV stabilizers, lubricants, mold-release agents,dyes, pigments and flame retardants.

Examples of oxidation inhibitors and heat stabilizers which may be addedto the thermoplastic molding compositions according to the invention arehalides selected from the group consisting of metals in group I of thePeriodic Table, such as lithium halides, sodium halides, potassiumhalides and copper(I) halides, for example chlorides, bromides andiodides, or mixtures of these. It is also possible to use stericallyhindered phenols, secondary aromatic amines, hydroquinones, substitutedrepresentatives of this group and mixtures of these compounds,preferably in concentrations of up to 1% by weight, based on the weightof the mixture.

Examples of UV stabilizers are substituted resorcinols, stericallyhindered phenols, salicylates, benzotriazoles and benzophenones, whichcan generally be used in amounts of up to 2% by weight.

Examples of lubricants and mold-release agents, which generally can beadded to the thermoplastic molding compositions in amounts of up to 1%by weight, are long-chain fatty acids or their derivatives, such asstearic acid, stearyl alcohol, alkyl stearates and stearamides andpentaerythritol esters of long-chain fatty acids.

Examples of flame retardants are red and black phosphorus, or aphosphorus-containing compound, in amounts of from 3 to 10% by weight. Apreferred flame retardant is elemental phosphorus, in particular incombination with glass-fiber-reinforced molding compositions.

Other preferred flame retardants are organic phosphorus compounds, suchas the esters of phosphoric acid, of phosphorous acid, of phosphonicacid and of phosphinic acid, and tertiary phosphines and phosphineoxides, for example triphenylphosphine oxide. This may be used alone ormixed with hexabromobenzene or with a chlorinated biphenyl and, ifdesired, antimony trioxide.

Other suitable flame retardants are compounds which containphosphorus-nitrogen bonds, for example phosphonitrile chloride,phosphoric ester amides, phosphinic amides, tris(aziridinyl)phosphineoxide and tetrakis(hydroxymethyl)phosphonium chloride.

Organic dyes, such as nigrosin, pigments, such as titanium dioxide,cadmium sulfide, cadmium selenide, phthalocyanines, ultramarine blue andcarbon black may also be added as colorants.

Nucleating agents which may be used are sodium phenylphosphinate,alumina, silica, nylon-2,2 and, preferably, talc, usually in amounts ofup to 1% by weight.

Component A preferably has a tensile modulus >2000 MPa, particularlypreferably >2800 MPa, in particular >3500 MPa. The tensile modulus isdetermined here according to ISO 527 on single-component tensilespecimens.

Molding Composition B

Molding composition B is built up from

B1) from 20 to 79.9% by weight of at least one thermoplastic polyamide,copolyamide or blends of these, as component B1,

B2) from 20.1 to 80% by weight of at least one crosslinked elastomericpolymer as component B2 and

B3) from 0 to 30% by weight of other additives and processing aids ascomponent B3,

where the total of the amounts of components B1, B2 and, if desired, B3is 100% by weight.

The molding composition B contains, as component B1, from 20 to 79.9% byweight, preferably from 20 to 70% by weight, particularly preferablyfrom 25 to 55% by weight, in particular from 30 to 45% by weight, of atleast one thermoplastic polyamide, copolyamide or blend of these. Thepolyamides used may be those which are also used as component A1 in themolding composition A, particular preference again being given here tonylon-6,6 and nylon-6, especially nylon-6.

The molding composition B contains, as component B2, from 20.1 to 80% byweight, preferably from 30 to 80% by weight, particularly preferablyfrom 45 to 75% by weight, in particular from 55 to 70% by weight, of atleast one crosslinked elastomeric polymer.

The component B2 forms the disperse phase.

The molding composition B may contain, as component B3, up to 30% byweight, preferably up to 10% by weight, of other additives andprocessing aids. It is possible to use the additives and processing aidswhich are also present as component A4 in the molding composition A.

The Vicat softening point of the molding composition B, determinedaccording to ISO 306, method B, is preferably >180° C., particularlypreferably >200° C.

The tensile modulus of the molding composition B is generally from 50 to1500 MPa, preferably from 200 to 1000 MPa, particularly preferably from350 to 800 MPa.

Preferred crosslinked elastomeric polymers B2 are graft copolymers of

B21) from 50 to 97.9% by weight, preferably from 75 to 95.5% by weight,particularly preferably from 85 to 95% by weight, of at least oneolefinically unsaturated monomer as component B21,

B22) from 2 to 50% by weight, preferably from 4 to 25% by weight,particularly preferably from 8 to 15% by weight, of at least onepolyfunctional crosslinking monomer as component B22 and

B23) from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight,particularly preferably from 1 to 3% by weight, of at least oneolefinically unsaturated monomer having a group which is reactive topolyamide, as component B23.

Suitable olefinically unsaturated monomers for component B21 areC₁₋₁₀-alkyl (meth)acrylates, preferably C₁₋₈-alkyl (meth)acrylates,particularly preferably n-butyl acrylate and/or ethylhexyl acrylate.

The crosslinking monomers B22 are polyfunctional monomers having atleast two ethylenically unsaturated groups. Of these, preference isgiven to polyfunctional, in particular difunctional compounds havingnon-conjugated double bonds, for example divinylbenzene, diallylfumarate, diallyl maleate, diallyl phthalate, triallyl cyanurate,triallyl isocyanurate, tricyclodecenyl acrylate anddihydrodicyclopentadienyl acrylate, of which the last two areparticularly preferred.

Particularly suitable olefinically unsaturated monomers B23 having agroup reactive to polyamide are acrylic acid, methacrylic acid, maleicacid, maleic anhydride, fumaric acid and glycidyl methacrylate, inparticular acrylic acid and methacrylic acid.

The elastomeric polymer is preferably a core-shell polymer, ie. apolymer built up from a core (graft base) and one or more shells(graft). The graft base preferably has only components B21 and B22, andcomponent B23, which has groups reactive to polyamide, is present onlyin the shell. This structure ensures that the groups which bring aboutadhesion to component B1 are present also at the surface of the polymerparticles.

In a preferred embodiment of the invention, crosslinked acrylatepolymers having a glass transition temperature of below 0° C.,preferably below −20° C., in particular below −30° C., serve as graftbase.

Suitable processes for preparing the graft base A1 are known per se andare described, for example, in DE-B-1 260 135. Corresponding productsare also available commercially. Preparation by emulsion polymerizationhas proven especially advantageous.

The precise polymerization conditions, in particular the type, method ofaddition and amount of the emulsifier, are preferably chosen so that thelatex of the acrylate, which is at least to some extent crosslinked, hasa mean particle size in the range from 10 to 10 000 nm, preferably from100 to 1000 nm. The latex preferably has a narrow particle sizedistribution.

The graft shell is preferably prepared in emulsion, as described, forexample, in DE-B-12 60 135, DE-A-32 27 555, DE-A-31 49 357 and DE-A-3414 118.

Shaped Articles

In a preferred embodiment of the invention, the shaped articles consistof molding compositions A and B whose tensile modulus differs by afactor of at least 2.

In a further preferred embodiment, the molding compositions A and Bcontain the same polyamide as components A1 and B1.

The mixing of components A1 to A4 to give molding composition A and ofcomponents B1 to B3 to give molding composition B may be carried out byknown methods. The components are preferably mixed by jointly extrudingor compounding them.

For this, it is expedient to use extruders, such as single-screw ortwin-screw extruders, or other conventional plastication equipment, suchas Brabender mixers or Banbury mixers.

The product of the graft copolymerization (component B2), which isobtained in aqueous dispersion, may, before mixing, be dried completely,for example by spray drying, and mixed as pulverulent polymer with theother components. However, as described in DE-A-33 13 919, it is alsopossible to use the aqueous polymer dispersion, preferably firstlyplasticating the polyamide in the mixing equipment. When the polyamidemelt is mixed with the polymer dispersion, the water evaporates, and therubber particles become uniformly distributed in the melt.

Known processes, for example injection molding, extrusion or extrusionblow molding, may be used for producing the shaped articles from themolding compositions A and B.

The shaped articles may, for example, be produced by injection molding.For this, the molding compositions A or B may be molded onto, orextruded onto, a hardened section of the other molding composition ineach case. The shaped articles may also be produced by two-componentinjection molding, with simultaneous injection of the two moldingcompositions A and B, preferably from opposite ends of the injectionmold.

The production of shaped articles by injection molding is preferablycarried out using molding compositions A and B which contain, aspolyamide components A1 and B1 respectively, polyamides having aviscosity number of from 140 to 185.

The molding compositions A and B are particularly advantageously usedfor producing hollow shaped articles. Hollow shaped articles made fromdifferent molding compositions A and B are generally produced bycoextrusion of the molding compositions A and B, the extrusion die beingfed from at least two different extruders. A tube is extruded whichcontains both molding compositions A and B. The extruded tube may itselfbe the desired shaped article, such as a straight pipe, or may be aparison from which the shaped article is produced by further processsteps.

In coextruding the hollow shaped article or parison, it is possible tooperate with constant rates of material flow from each extruder. Thisgives an extruded tube which has, distributed through the thickness ofthe wall, a sequence of layers of identical or different thickness of,in each case, one of the molding compositions A or B, the layerthickness and the construction remaining constant over the entire lengthof the tube.

It is, however, more advantageous to produce the hollow shaped articlesor parisons by sequential coextrusion, ie. with alternating materialflows. This can be carried out by feeding the extrusion die fromalternating extruders, ie. alternately solely with molding composition Aor molding composition B. This gives a tube which has an alternatingconstruction along its entire length, with segments of, in each case,only one of the molding compositions A or B. The switching from oneextruder to the other may be sudden or may occur continuously within alimited period of time. In the latter case, a limited portion of thetube (in contrast to the entire length of the extruded tube) has layersof both molding compositions, the layer thickness ratio changingcontinuously from 100% of the molding composition A (B) to 100% of themolding composition B (A). This achieves a surface bond between theindividual segments of the hollow shaped article or parison, resultingin a marked improvement in the adhesion between the segments.

In a preferred embodiment of the invention, there is no completeswitching from one molding composition to the other. This gives shapedarticles which have, along their entire length, both layers of,respectively, molding composition A and B; the sequence of the layershere from outside to inside may be as desired. By this means it ispossible to obtain hollow shaped articles made from hard and softsegments of different layer thickness ratio. In principle, any desiredratio of layer thicknesses may be selected for each segment. Theproportion of the layer of molding composition A in the wall thicknessin the hard segments of the shaped articles is generally from 70 to99.9%, preferably from 70 to 99%, particularly preferably from 80 to95%, in particular from 85 to 90%, and in the soft segments of theshaped articles it is generally from 0.1 to 30%, preferably from 1 to30%, particularly preferably from 5 to 20%, in particular from 10 to15%, where in each case the proportion of the layer of moldingcomposition B is such as to give a total of 100%. The change of layerthicknesses between the hard and soft segments is preferably not sudden,but continuous across a length which, for example, corresponds to 5times the wall thickness.

It is also possible to extrude parisons or shaped articles which havemore than just two layers; the sequence of the layers here from outsideto inside may be as desired, and the thickness of the individual layersmay vary. For example, the shaped articles may have a structure in whichthree layers have the sequence A-B-A or B-A-B. The shaped articles mayalso have segments having a different number of layers.

The novel shaped articles preferably have two layers.

Coextrusion may be combined with other process steps known per se forproducing hollow shaped articles having shapes diverging from that of asimple tube (straight and with constant diameter along the length). Thehollow shaped articles may, for example, be produced by extrusion blowmolding. For this, the tube is extruded into an opened mold, the mold isclosed and the tube is expanded. In the molding step, the walls of theparison are pressed by the internal gas pressure against the inner wallof the mold, and solidify.

The molding may also be carried out by firstly expanding the parison andthen closing the mold. This generally gives hollow shaped articles withan encircling pinch-off line.

In producing the novel shaped articles, molding by expanding the parisonis preferably carried out after closing the mold.

Hollow shaped articles of complicated shape can also be produced bycombining blow molding and a technique known as 3D extrusion. For this,a tube is extruded and placed, with shaping as required by the contoursof the shaped article, into the half of an opened mold. The placing ofthe tube may, for example, be carried out by moving the opened blowingmold under the extruder, by moving the extruder over the opened blowingmold or by manipulating the extruded tube using a grab arm. The blowingmold is then closed and the tube is expanded. The extruded tube may alsobe sucked into the blowing mold and expanded. Processes for 3D extrusionand/or tube manipulation are known to the person skilled in the art. Thehollow shaped articles obtained have complicated shapes and noencircling pinch-off line.

The molding compositions A and B used for producing hollow shapedarticles by simple (co)extrusion without subsequent blow moldingpreferably have, as components A1 and/or B1, polyamides having aviscosity number of from 190 to 285.

The molding compositions A and B used for producing hollow shapedarticles by extrusion followed by blow molding preferably have, ascomponents A1 and/or B1, polyamides having a viscosity number of from250 to 400.

In a preferred embodiment of the novel process, hollow shaped articlesare produced by 3D extrusion followed by blow molding. By this means itis possible to produce blow-molded parts having flexible end zones and ahard middle section. Typical applications are especially parts forautomotive construction and mechanical engineering. Examples are airintake pipes or air ducts, which, for ease of assembly and end-sealingon the one hand, and adequate resistance to reduced and/or increasedpressure in the middle section on the other hand, require asoft-hard-soft combination.

The novel shaped articles have the advantage that, although thestiffness of their segments differs, other properties which aresignificant in applications are retained along the entire length of theshaped article, ie. both in the hard and in the soft segments.

Thus, molding composition B, although it may have a high proportion ofolefin polymer, has the properties typical of polyamides, such as highheat resistance and good solvent resistance, and as a result, theseproperties are also present in the soft segments (which have a highproportion of molding composition B). The tensile strength of componentB is also comparatively high, and therefore the novel shaped articleshave high bursting strength along their entire length.

It is particularly noteworthy that, in the novel shaped articles,segments of different construction and having different combinations ofproperties are combined without the need for intermediate layers ofadhesion promoters. Intermediate layers of this type are generallyundesirable, since they increase the number of transitions betweenmaterials. Intermediate layers of the usual adhesion promoters moreoverare points of weakness with respect to heat resistance and chemicalresistance (solvent resistance).

It is also particularly noteworthy that the novel shaped articles have ahigh long-term service temperature and good resistance to heat aging.They are therefore particularly suitable for applications in the motorvehicle sector, in particular for internal use in motor vehicles, forexample as pipelines for gas or liquid in the engine compartment.

In a particularly preferred embodiment of the invention, hollow shapedarticles are produced in the form of air and coolant ducts for motorvehicles.

The invention is described in more detail by means of the followingexamples.

EXAMPLES

In the examples, use was made of two-component tensile specimens madefrom the molding compositions A and B and of single-component tensilespecimens made from, in each case, one molding composition.

The two-component tensile specimens (thickness: 4 mm, length: 160 mm,width in the central section: 10 mm) were produced by injection-moldingthe molding compositions A and B at 270° C., using an Arburgtwo-component injection-molding machine, to give standard tensilespecimens of the dimensions given in ISO 527. The tensile specimens herewere injection molded with one component from each side, with the resultthat the dividing line between A and B fell approximately in the centerof the tensile specimen. It could be seen without difficulty because ofthe different pigmentation of the components.

One-component tensile specimens were also injection molded from therespective components by a standard method.

The tensile strength of the two-component tensile specimens wasdetermined; (fracture always occurred at the interface).

The tensile modulus of the single-component tensile specimens, and theirultimate tensile strength, were determined according to ISO 527, andtheir Vicat softening point (method B) was determined to ISO 306. Partsmade from the respective molding compositions were also refluxed for 6 hin toluene, and the uptake of solvent determined. The results are givenin the following table.

The molding compositions used had the following formulation:

Example 1

Molding composition A made from nylon-6 having 30% by weight ofglass-fiber reinforcement, viscosity number (VN)=142 ml/g (UltramidB3WG6 from BASF AG, Ludwigshafen, Germany)

Molding composition B made from 42% by weight of nylon-6, VN=150(Ultramid B3 from BASF AG) and 58% by weight of a dispersion rubber madefrom n-butyl acrylate with 8% of dicyclopentadienyl acrylate (DCPA) ascrosslinker, graft shell of methyl methacrylate with I% by weight ofmethacrylic acid, having a particle size of 0.1 μm, compounded at 280°C. using a twin-screw extruder (ZSK 30 from Werner & Pfleiderer) at 200rpm and a throughput of 12 kg/h.

Example 2

as Example 1, but molding composition A made from nylon-6 reinforcedwith 15% by weight of glass fibers, VN=175 mug (Ultramid B35WG3 fromBASF AG)

Example 3

as Example 1, but molding composition A made from unreinforced nylon-6,VN=180 ml/g (Ultramid B35W from BASF AG)

Example 4

Molding composition A made from unreinforced nylon-6, VN=330 ml/g(Ultramid B6W from BASF AG)

Molding composition B made from 42% by weight of nylon-6, VN=250(Ultramid B4 from BASF AG) and 58% of the dispersion rubber of Example 1

Example 5

as Example 4, but molding composition B made from 35% by weight of thepolyamide and 65% by weight of the dispersion rubber

Example 6

as Example 4, but molding composition B made from 55% by weight of thepolyamide and 45% by weight of the dispersion rubber

Example 7

as Example 4, but molding composition B made from 70% by weight of thepolyamide and 30% by weight of the dispersion rubber

Example 8

as Example 4, but molding composition A made from nylon-6 reinforcedwith 20% by weight of glass fibers, VN=300 (Ultramid KR 4465 G4 fromBASF AG)

Comparative Example C 1

as Example 4, but molding composition B made from 90% by weight of thepolyamide and 10% by weight of the dispersion rubber

Comparative Example C 2

as Example 4, but molding composition B made from 42% by weight of thepolyamide and 58% by weight of a dispersion rubber which is notcrosslinked and whose core is of 100% by weight of n-butyl acrylate, andwhose shell is of 99% by weight of n-butyl acrylate and 1% by weight ofmethacrylic acid.

Comparative Example C 3

as Example 4, but molding composition B made from 42% by weight of thepolyamide and 58% by weight of an ethylene-propylene copolymer having30% by weight of ethylene, grafted with 0.8% by weight of maleicanhydride (Exxelor VA 1803 from EXXON Chemicals) as soft polymer

Comparative Example C 4

as Comparative Example C 2, but molding composition B made from 70% byweight of the polyamide and 30% by weight of the soft polymer

Comparative Example C 5

as Example 4, but molding composition B made from 42% by weight of thepolyamide and 58% by weight of a copolymer of 63% by weight of ethylene,35% by weight of butyl acrylate and 2% by weight of acrylic acid(Lotader 4700 from Atochem) as soft polymer

Comparative Example C 6

as Comparative Example C 4, but molding composition B made from 70% byweight of the polyamide and 30% by weight of the soft polymer

Example 10

A modified two-component blow-molding system having two 90 mm extrudersand one 45 mm extruder was operated with, on one of the 90 mm extruders,a molding composition A made from nylon-6, VN=310 ml/g (Ultramid B6Wfrom BASF AG), and, on the second 90 mm extruder, a molding compositionB made from a compounded mixture of 42% by weight of nylon-6, VN 285(Ultramid B4 from BASF AG) and 58% by weight of a dispersion rubber madefrom n-butyl acrylate with 4% of crosslinker, graft shell made frommethyl methacrylate with 1% by weight of methacrylic acid (Paraloid 3387from Rohm & Haas); the 45 mm extruder was not in operation. By modifyingthe control arrangements, the throughput of the two extruders could beswitched between the operating conditions:

Operating

condition 1: Extruder 1=54 kg/h, Extruder 2=6 kg/h

Operating

condition 2: Extruder 1=6 kg/h, Extruder 2=54 kg/h

The total throughput was 60 kg/h and the processing temperature in bothextruders was 250° C. The output was a 1500 mn tube having an outerlayer of the molding composition A and an inner layer of the moldingcomposition B, and this was expanded to give a straight, rectangularhollow shaped article of 120 mm×120 mm cross section and 720 mm length.The wall thickness was from 3 to 5 mm. Hard segments made from 90% byweight of molding composition A (outside) and 10% of molding compositionB (inside) were extruded at the start and at the end of the tube, and inthe middle a soft segment, 150 mm in length, made from 10% by weight ofthe molding composition A (outside) and 90% by weight of the moldingcomposition B (inside). Each transition between the two layer thicknessdistributions occurred over a longitudinal section of at least 20 mm.

Example 11

as Example 10, but with a molding composition A made from nylon-6,reinforced with 20% by weight of glass fibers, VN=300 (Ultramid KR 4465G4 from BASF AG)

The hollow shaped articles obtained had uniform surfaces and goodadhesion between the segments.

TABLE 1 Tensile Tensile Tensile Tensile Solvent modulus strength modulusstrength 2-component VSP (method VSP (method uptake molding moldingmolding molding tensile B) molding B) molding molding Solvent uptake Ex.comp. A comp. A comp B. comp. B strength comp. A comp. B comp. A moldingcomp. B 1 8000 185 800 35 32 225 195 <1% 11.5 2 4800 155 800 35 32 225195 <1% 11.5 3 3050 90 800 35 33 219 195 <1% 11.5 4 2950 85 800 35 33219 195 <1% 11.5 5 2950 85 620 30 29 219 185 <1% 14.0 6 2950 85 1145 4136 219 201 <1% 10.0 7 2950 85 1450 50 48 219 205 <1%  7.9 8 5000 160 80035 30 225 195 <1% 11.5 C1 2950 85 2480 57 55 219 212 <1%  2.9 C2 2950 85245 12 10 219 212 <1% destroyed C3 2950 85 200 10 8 219 65 <1% destroyedC4 2950 85 1370 55 50 219 179 <1% 12.0 C5 2950 85 250 10 10 219 59 <1%destroyed C6 2950 85 1410 58 52 219 182 <1% 11.0 VSP = Vicat softeningpoint

We claim:
 1. A hollow shaped article having hard and soft segments madefrom a) from 5 to 95% by weight of a molding composition A composed ofa1) from 40 to 100% by weight of at least one thermoplastic polyamide,copolyamide or blends of these as component A1, a2) from 0 to 60% byweight of fillers and/or reinforcing materials as component A2, a3) from0 to 20% by weight of impact modifiers as component A3 and a4) from 0 to30% by weight of other additives and processing aids as component A4,where the total of the amounts of component A1 and, if used, A2 to A4,is 100% by weight, b) from 5 to 95% by weight of a molding composition Bcomposed of b1) from 20 to 70% by weight of at least one thermoplasticpolyamide, copolyamide or blends of these as component B1, b2) from 30to 80% by weight of at least one crosslinked elastomeric polymer ascomponent B2 and b3) from 0 to 30% by weight of other additives andprocessing aids as component B3, where the total of the amounts ofcomponents B1, B2 and, if used, B3 is 100% by weight, wherein the wallof the hollow shaped article has a sequence of layers of the moldingcompositions A and B from outside to inside, wherein the proportion ofthe layer of molding composition A in the wall thickness in the hardsegments is from 70 to 99.9% and in the soft segments is from 0.1 to30%, where in each case the proportion of the layer of moldingcomposition B is such as to give a total of 100%.
 2. The hollow shapedarticle of claim 1, where the molding composition A has one or more ofthe following features: component A1 comprises nylon-6 and/or -6,6,component A2 consists of glass fibers, component A4 comprises heatstabilizers, the viscosity number of component A1 is from 130 to 500,the tensile modulus of molding composition A is >2000 MPa.
 3. The hollowshaped article of claim 1, where the molding composition B has one ormore of the following features: component B1 comprises nylon-6 and/or-6,6, component B3 comprises heat stabilizers, the tensile modulus ofmolding composition B is from 50 to 1500 MPa, the Vicat softening point(method B) of molding composition B is >180° C.
 4. The hollow shapedarticle of claim 1, wherein emulsion copolymers of b21) from 50 to 97.9%by weight of at least one C₁₋₈-alkyl acrylate, as component B21, b22)from 2 to 50% by weight of at least one polyfunctional crosslinkingmonomer having at least two ethylenically unsaturated groups, ascomponent B22 and b23) from 0.1 to 10% by weight of at least oneolefinically unsaturated monomer having a group which is reactive topolyamide, selected from the group consisting of acrylic acid,methacrylic acid, maleic acid, maleic anhydride, fumaric acid andglycidyl methacrylate, as component B23, where the sum of the amounts ofcomponents B21, B22 and B23 is 100% by weight, having one or more of thefeatures: B2 is a core-shell polymer, the reactive groups are presentonly in the shell, the glass transition temperature of the core is <0°C., the particle size is from 0.01 to 10 μm are used as component B2. 5.The hollow shaped article of claim 1, having at least one of thefeatures: the tensile modulus of molding compositions A and B differ bya factor of at least 2 and molding compositions A and B comprise thesame polyamide.
 6. The hollow shaped article of claim 1 in the form ofan air coolant duct for motor vehicles.
 7. The hollow shaped article ofclaim 1, wherein the wall of the hollow article has, at least to someextent, a sequence of layers of the molding compositions A and B fromoutside to inside, the sequence from outside to inside being A-B and/orB-A.
 8. The hollow shaped article of claim 1, wherein moldingcomposition A is composed of from 10 to 60% by weight of fillers and/orreinforcing materials as component A2.
 9. A process for producing ahollow shaped article from molding compositions A and B, as the aredefined in claim 1, by co-extrusion, where components A1 and B1 have aviscosity number of from 190 to 285, or co-extrusion blow molding, wherecomponents A1 and B1 have a viscosity number of from 250 to
 400. 10. Aprocess for producing a hollow shaped article as it is defined in claim1 by co-extrusion of molding compositions A and B.
 11. A process forproducing a hollow shaped article as it is defined in claim 1 bycoextrusion or coextrusion blow molding of molding compositions A and B.